Clutch mechanism



H. D. COLMAN 2,091,269

CLUTCH MECHANI S M Aug. 31, 1937.

7 Sheets-Sheet 1 Filed March 5, 1954 INVENTQR Howard D. Colman ATTORNEYS BY V %M Fm; Mm

Aug. 31, 1937. H. D. COLMAN 2,091,269

CLUTCH MECHANISM Filed March 5, 1934 7 Sheets-Sheet 2 I un] 1 II III :|u ||m| 1 H" INVENTOR Howard D. Colman BY :4. g x a ATTORNEYS Au 31, 1937. H. D. COLMAN 2,091,269

CLUTCH MECHANI SM Filed March 5, 1934 7 Sheets-Sheet 3 INVENTQR Howard D. Colman- BY ATTORNEYIS g- H. D. COLMAN 2,091,269

CLUTCH MECHANISM Filed March 5, 1934 7 Sheets-Sheet 4 l/llllllllll Will INVENTO Howard D. lman BY W M x @040.

ATTORNEYS Aug. 31, 1937. H. D. COLMAN QLUTCH MECHANISM Filed March 5, 1934 7 Sheets-Sheet 5 INVENTOR Howard .D. Colman ZHM W "Ma-r- ATTORNEYS Aug. 31, 1937. H. D. COLMAN 2,091,269

' CLUTCH MECHANISM Filed March 5, 1934 7 sheets-sheet s 9 INVENTOR W M In Mm ATTORNEYS Aug. 31, 1937. D, CQLMAN 2,091,269

CLUTCH MEGHANI SM Filed March 5, 1954 7 Sheets-Sheet 7 INVENTOR Howard D. Colman awwxw ATTORNEYS Patented Aug. 31, 1937 -UNITED STATES PATENT OFFICE 34 Claims.

The present invention relates to a new and improved clutch mechanism which is adapted particularly for use in motor vehicles, and to provide either a conventional drive or free wheeling at the option of the user.

Free wheeling is commonly obtained by the use of an automatic clutch adapted to be opened by the suction of the motor whenever the throttle pedal is released, or by the use of an over-rum ning clutch in series with an ordinary clutch, and adapted to permit the speed of the vehicle to exceed that of the motor.

Each form is subject to certain disadvantages.

'Thus, the automatic clutch, although affording free wheeling or coasting with the motor operating at an idling speed. when the throttle pedal is up, will close immediately under full pressure whenever the throttle pedal is partially depressed regardless of whether or not the speeds of the driving and driven clutch elements are synchronized. Usually the clutch elements are not synchronized in speed and hence the closing of the clutch results in a decidedly noticeable shock which detracts from the smooth riding qualities of the vehicle, and which produces excessive wear on the friction plates. If the closing of the automatic clutch were to be delayed, there would still be no assurance of synchronism.

The over-running clutch is not subject to the '30 foregoing disadvantages since, if the throttle pedal is depressed to accelerate the motor, it will engage only when the speed of the driving element reaches and starts to exceed that of the normally driven element. However, the over-running clutch alone does not permit gear shifting, without the use of the clutch pedal, except into intermediate and high speed positions, and is incapable of utilizing the motor as a brake when going down steep hills, or of providing a reverse drive 40 connection. Hence, a third clutch, usually a positive jaw clutch or its equivalent, adapted to drive in either direction, is provided for connecting the power drive around the over-running clutch at the option of the user. This third clutch is manually operable, and if closed when the relative speed of the driving and driven elements is substantial will cause a violent shock.

Neither one of the two clutches ordinarily employed for free wheeling therefore affords all of the advantages of the other. Hence, both types of free wheeling clutches have in some instances been incorporated as separate units in the same vehicle drive, and have been placed under a manual dash control whereby to obtain a conventional drive, or free wheeling by the use of the advantages and operating functions of both the 10 usual automatic clutch and over-running clutch, and adapted for use also in the conventional drive.

A further object is to provide a new and improved clutch mechanism of the foregoing char- 15 acter including a time device when set for free wheeling which is automatically operable to delay the engagement of the clutch when the throttle pedal is initially depressed until the motor has had an opportunity to accelerate, and which may 20 be rendered ineffective by depressing the clutch pedal to eliminatev the delay when desired, or varied in effectiveness by the position of the throttle pedal to vary the delay in accordance with the motor speed, thereby placing the time 25 and rate of clutch engagement under the full control of the operator.

A further object is to provide a novel unitary clutch mechanism which is selectively available ,for free wheeling or a conventional drive, and in which the conversion from the former to the latter may be accomplished without any possibility of shock, unless it becomes necessary in an emergency to immediately utilize the braking action of the motor. In the latter event, the 35 shock is never as great as that resulting when closing a positive clutch to out out the usual overrunning clutch unit.

Another object resides in the provision of a novel time device in one form of the invention which does not affect the delay in clutch engagement through the actuation of mechanical parts.

Still another object resides in the provision of a new and improved clutch mechanism of the foregoing character in which the pressure of clutch 45 engagement, when under the control of the throttle pedal as in free wheeling, is automatically varied in accordance with the position of the pedal and therefore with the torque of the motor, and, when under the sole control of the clutch 50 pedal as in the conventional drive, is subject to a finely graduated variation over substantially the entire stroke of the clutch pedal so as to permit accurate control of any desired degree of clutch slippage. 55

A further object resides in the provision of a novel clutch mechanism adapted for use in the conventional drive of a motor vehicle under the control of a clutch pedal in which very little effort is required to actuate the pedal.

Another object is to provide a new and improved clutch mechanism adapted for various purposes, and more particularly having a main clutch, and a pilot clutch operable in either direction through an anti-friction screw device to close the main clutch. Other detailed objects reside in the provision of one or more of the following, namely: an electromagnetic pilot clutch in the foregoing combination which is self-adjustable to compensate for wear, and which may be rendered adjustable to vary its power upon reversal in torque; ball bearing splines for centering and guiding each movable element of the main clutch; and novel means for preventing lubricant from entering between the coacting surfaces of the main and pilot clutches.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings, Fig. 1 is a fragmentary axial sectional view of a clutch mechanism with a'main clutch and an electromagnetic pilot clutch, embodying the features of my invention.

Fig. 2 is a fragmentary cross-sectional view of the main clutch taken substantially along line 2-2 of Fig. 1. r

Fig. 3 is a fragmentary plan view of the main clutch, partially in section substantially along 35 broken line 3-3 of Fig. 2.

Fig. 4 is a fragmentary perspective view of the pilot clutch, and illustrates the mounting of the electromagnet.

Fig. 5 is a fragmentary transverse sectional 40 view of the pilot clutch taken substantially along line 5-5 of Fig. 1.

Fig. 6 is a fragmentary plan view of the pilot clutch, partially in section along line 66 of Fig. 1 through a switch on the electromagnet.

45 Fig. 7 is a fragmentary transverse sectional view taken substantially along line 1--1 of Fig. 6.

Fig. 8 is a fragmentary sectional detail view taken along line 8-8 of Fig. 6, and illustrating contact brushes in the electric circuits for the 50 electromagnet.

Fig. 9 is a view ,on 'an enlarged scale of a ball screw device forming part of the means for actuating the main clutch.

Fig. 10 is a fragmentary perspective view of the 55 main clutch actuating means, with the elements of the ball screw device in disassembled relation.

Fig. 11 is a fragmentary transverse sectional view taken substantially along line of Fig. 1, and illustrating means for equalizing the pres- 0 sure on the balls in the screw device.

Fig. 12 is a perspective view of a retainer for the balls between the threads of the screw device. and the means for limiting its motion.

Fig. 13 is a side view of an automobile provided 65 with a clutch mechanism embodying the features of the present invention.

Fig. 14 is a diagrammatic representation of the electrical control apparatus for the pilot clutch. i Fig. 15 is a diagrammatic representation of a 70 modified mechanical control mechanism for the pilot clutch.

Fig. 16 is a fragmentary detail view of the mechanism shown in Fig. 15.

Fig. 1'? is a detail sectional view.

Referring more particularly to the drawings,

the clutch mechanism constituting the exemplary embodiment of the invention is mounted within a suitable housing 20, and is interposed between a driving shaft 2| and a driven shaft 22. Within the broad aspects of the invention, the clutch mechanism may be adapted for various purposes. However, it is particularly suited for, and hence is disclosed as incorporated in the power plant of an automobile or other motor vehicle. Thus, the driving shaft 2| is the crank shaft of a motor 23 (see Fig. 13), and the driven shaft 22 is adapted to be connected through a change-speed gear box 24 to a transmission shaft 25 extending to the rear of the vehicle. As shown, the clutch housing 20 is secured in position between the crank case of the motor 23 and the gear box 24.

The clutch mechanism generally comprises a main clutch 26 having driving and driven elements 21, 21 and 28 which are adapted to be moved into and out of coacting engagement, and which are secured respectively to the shafts 2| and 22 for rotation therewith. The main clutch 2B is normally open, i. e. the coacting elements thereof are yieldably urged apart, and is adapted to be closed by a pilot clutch 29 acting through an anti-friction screw device 30. This device comprises a rotatable screw 3| and a nut 32 threaded thereon for axial movement. The nut 32 is operatively connected to the movable clutch element 21, 21, and is adapted upon movement in opposite directions out of a neutral or intermediate position to move one or the other of the clutch elements into gripping engagement with the element 28. The screw 3| and nut 32 are urged into relative neutral position by the opening action of the clutch 26, and rotate as a unit with the driving element 21, 21. The pilot clutch 29 comprises coacting clutch elements 33 and 34 secured respectively to the driven shaft 22 and the screw 3|. When the pilot clutch 29 is closed, a rotational drag resulting from the positive or negative rotation of the shaft 22 relative to the shaft 2| is applied to the screw 3|, thereby causing relative rotation between the screw and the nut 32 to close the main clutch. When the clutch mechanism is converted to effect free wheeling, the drag in one direction which would result if the shaft 22 were to overrun the shaft 2|, is reduced to such an extent that it is incapable of overcoming the opening action of the main clutch 26.

The engine crank shaft 2| (see Fig. 1) extends into one side of the housing 20, and the inner end thereof is formed with an axial bore 35 and with an annular peripheral flange 36. A flywheel 31 in the form of an annular disk having a rim 38 on one side is securely bolted to the flange 36. The driven shaft 22 extends through a bearing sleeve 39 in the other side of the housing 20, and has a reduced inner end 40 supported in a bushing 4| within the bore 35. Thus, the shafts 2| and 22 are mounted in coaxial relation, with the shaft 22 extending substantially through the housing 20 and telescopically supported by the shaft 2|.

The main clutch 26 may be provided in various forms, but preferably is of the friction disk type in which the driven element 28 consists of a single plate splined for axial movement on the shaft 22, and provided on opposite sides with friction rings 42, and in which the driving element 21, 21 consists of two parallel annular plates mounted on the flywheel 31 respectively at opposite sides of the plate 28 for axial movement into coacting engagement with the friction rings 42. A sleeve 43 axially splinedon the driving 6 The movable clutch plates 21 have'an anti-,

friction axial spline connection with the flywheel 31 (see Figs. 1 and 2). Thus, a plurality of uniformly peripherally spaced opposed recesses or bores 45 and 45' are formed respectively to intersect the inner surface of the rim 38 and the outer surfaces of the clutch plates 21. Hardened steel inserts 48 and 41 are securely fitted in the recesses 45 and 48', and are formed respectively with coacting V-shaped raceways 48 and 48 parallel to the axis. In the present instance, two sets of raceways 48 and 48 located in diametrically opposed relation are provided. Disposed respectively between the inner raceways 49 and the coacting outer raceways 48, and in bearing engagement therewith, are a plurality of balls 58. The flywheel 31 and a flat annular plate 5| secured to the free end of the rim 38 serve to prevent outward displacement of the balls 58. Disposed between the clutch plates 21 and the rim 38 and held endwise between the flywheel 31 and the end plate 5| are two spacer plates 82. Each of the plates 52 is formed in opposite ends with longitudinal slots 83 freely receiving the associated set of balls 58, and serving to prevent accidental inward displacement thereof. The ball bearing splines just described serve to center the clutch plates 21 relative to the flywheel'31. They'also prevent relative angular motion between the clutch plates 21 and the flywheel 31, but permit free independent axial movement of each plate without any appreciable friction.

Normally the movable clutch plates 21 are yieldably pressed apart, and out of engagement with the intermediate clutch plate 28. against 40 two sets of peripherally spaced stops 54 and 55 mounted respectively in the flywheel31 and the plate 5|. These stops, although not essential, are desirable becausethey prevent direct contact over a large surface area between the clutch 45 plates21 and the flywheel 31 and plate 5|. If they were not provided, fine powder "resulting from wear on the friction rings 42 might work in between these parts, and tend to prevent complete opening of the clutch 28. The stops 54 and 50 55 project inwardly a slight distance from their respective supports and are small in bearing area, so that there is practically no chance of powder or .dust to lodge thereon and prevent the opening of the clutch to any material extent. I

Preferably, the yieldable means (see Figs. 2 and 3) for opening the clutch 28 comprises a. plurality of uniformly peripherally spaced coil compression springs 58 disposed between the movable plates 21. The outer peripheral margins of the 60 plates 21 projectbeyond the outer periphery of the intermediate plate 28, and are formed in their adjacent sides with a plurality of opposed recesses or spring seats 51 in which opposite ends of the springs 56 are seated.

A single actuator is provided for moving the clutch plates 21 against the action of the springs 58 into engagement with the intermediate plate 28 to close the clutch 28. In the present instance. this actuator comprises a flat annular 70 plate 58 disposed about and. movable in either direction axially of the driven shaft 22. Anchored in uniformly spaced relation to the actuator plate 58 adjacent its outer periphery, and extending in the direction of adjustment thereof, 75 are a plurality of parallel studs 59 which project satisfactory lead may be provided.

through openings-88 in theplate8l, The free end of each stud '88 has a portion of reduced diameter which projects through aligned openings 8| in the movable clutch plates 21 between 1 the springs 58, and which "at one'end defines an annular shoulder 82 for engaging the outer face of one of the clutch plates, and at the other end has a nut 83 threaded thereon for engaging the outer face of the other clutch plate. The nuts;83 are freely disposed in openings '84 in the flywheel 31. It will be evident that upon adjustment of the actuator plate 58 to the right as viewed in Fig. 1, the nuts 83 W11 compress and hold the clutch plates 21 and 28 in frictional engagement and as a unit against the adjacent stops 58v to close the clutch 28. Conversely, upon adjustment of the actuator plate 88in the opposite direction. the shoulders 82 will press theclutch plates 21 and 28 against the adjacent stops 84. Thus, adjustment of the actuator plate 58 out of neutral in either direction will establish a driving connection between the shafts 2| and 22. Since the studs 58 extend through the plates 21 and 28, the actuator plate 58 is constrained to rotate with the flywheel 31.

The actuator plate 58 is adapted to be operated by the pilot clutch 29 through the anti-friction screw device 30 (see Figs. 9 to 12). The screw 3| and nut 32 of the device 38 are formed re spectively with complementary screw threads 64 and 85. Preferably, the. device 30 has a triple thread with a lead approximately equal to the outside diameter of the screw 3|. although any suitable number of threads and threads of any Interposcd between the inner and outerthreads 84 and 85 are a plurality of balls 88. In the present instance, one ball 88 is provided for each thread .84 of the prises an annular ring 88 secured to one end of the nut 32 and close y encirc ing the screw 3|. A lug 89 on one end of the cage 81 projects into an arcuate notch 10 formed in the inner periphery of the ring 88. The opposite end faces of the notch 10 constitute s aced stops 1| and 12 adapted to coact with the lu 89 to limit the degree of rotation of the cage 81 in both directions.

The screw 3| is formed ntegral with an elongated sleeve 13 which is freely disposed about the driven shaft 22, and which is supported in a fixed axially suspended posi ion on the flywheel 31 by an end-thrust bearing 14 (see Fi 1). The latter comprises "an inner sleeve 15 rigidly secured on one end of the sleeve 13, and formed in its outer periphery with an annular groove or raceway 18, and an outer concentric sleeve 11 rigidly secured to the plate 5|, and formed in its inner periphery with a complementary groove or raceway 18. A plurality of balls 19 are interposed between the raceways 18 and 18 and in bearing engagement therewith. The balls 19 are held in uniformly spaced relation by a cage 80 loosely disposed between the sleeves 15 and 11. Preferably, the raceways 18 and 18 are non-circular in lateral section, so as toprovide a four point conscrew 3|, andthethree balls'are heldin uni- .formly spaced relation in acommon transverse 40 tact with each ball 19. The bearing 14 thus is of the type adapted to support a radial load, and also an axial thrust in either direction.

The nut 32 also is in the form of a sleeve, and

5 is connected to the actuator plate 58 for rotation and axial movement therewith. Preferably, the connection (see Figs. 1, 10, and 11) is self-adjusting to compensate for any misalignment of the plate 58 and to equalize the pressure on the balls 66. Thus, the connection comprises two equalizer rings 8| and 82 secured together in axially spaced relation, by means of a plurality of spacer bolts 83, and disposed against opposite sides of two outwardly projecting and diametrically op- 15 posed lugs 84 on the outer periphery of the nut 32. The bolts 83 are uniformly spaced about the periphery of the nut 32, and are provided in a number which is some multiple of four, as for example eight. The lugs 84 extend between adja- 0 cent bolts 83, and are of a width substantially equal to the spacing thereof so as to provide a rotary key connection between the nut 32 and the equalizer ring unit 8|, 82. The sides of the lugs 84 are rounded to permit a slight rocking motion of the equalizer ring unit about a diametrical axis. Two diametrically opposed lugs 85, on the inner periphery of the actuator plate 58, project between the rings 8| and 82 and between adjacent bolts 83 on a line perpendicular to that of the lugs 84. The lugs 85 are similar in form to the lugs 84, and serve to provide a rotary key connection between the plate 58 and the equalizer ring unit while permitting the plate to have a slight rocking motion about a diametrical axis perpendicular to that of the unit. Thus, the plate 58, although axially movable with the nut 32, is self-adjustable about two mutually perpendicular axes to compensate for misalignment and inequality in forces. As a result, the main clutch 26 is adapted to be closed with a uniform bearing pressure throughout its periphery.

It will be understood that when the main clutch 26 is open, the balls 68 in the screw device 38 act to cause the screw 3| to rotate with the nut 32 in a neutral or intermediate position. Rotation of the screw 3| relatively to the nut 32 in either direction, for example under-running because of a drag which may be termed "negative rotation, or over-running which may be called "positive rotation, will cause axial adjustment of the nut 32 and the actuator plate 58 in a corresponding direction to close the main clutch 26. The ball bearing screw device 38 and the ball spline for the plates 21 so nearly eliminate all friction that when the screw 3| is no longer subjected to a relative turning force, the springs 56 tending to open the clutch 26 are able to reverse the axial movement of the nut 32 along the screw to return the parts to their initial 80 positions.

The rotation of the screw 3| is controlled by the pilot clutch 29 (see Figs. 1 and 4 to 8) which preferably is of the electrc-magnetlc type. The element 34 of the clutch 29 comprises an annular 5 disk which is secured to the sleeve 13 by means of splines 86 and a clamp nut 81, and which is provided with a rim 88 formed in its outer periphery with a. plurality of uniformly spaced transverse keyways 89. An annular electromagnet 98 is mounted on and about the rim 88, and has a plurality of transverse keys 9| on its inner periphery projecting into the keyways 89. The keys 9| are somewhat narrower than the keyways 89, and hence permit the electromagnet 78 88 to have a limited angular motion on the rim 88. The inner ends of the keyways 89 open to a peripheral groove 92, one side of which constitutes a shoulder 93 (see Fig. 4) cooperating with an opposed retainer ring 94 to secure the electromagnet 98 against axial displacement. 5 The other element 33 of the pilot clutch 29 comprises a disk keyed in fixed position to the driven shaft 22. and an armature 95 mounted on the outer periphery of the disk in cooperative relation with the electromagnet 98. A suitable l0 spline connection is provided for effecting joint rotation of the disk 33 and the armature 95, but

permitting free axial movement of the latter. To

this end, the armature 95 is formed on its inner periphery with a plurality of uniformly spaced 15 keys 98 (see Fig. 5) slidably disposed in transverse keyways 91 formed in the outer periphery of the disk 33.

Also formed in and opening through the disk 33 between the respective keyways 91 are a plu- 20 raiity of transverse bores 98. These bores are so located that they intersect the outer peripheral surface of the disk 33, but that their axes fall substantially inside of the surface. A plurality of pins 99 are slidably disposed respectively in the 25 bores 98. Each of the pins 99 is formed intermediate the ends of the portion projecting cutwardly from the periphery of the disk 33 with a longitudinal notch |88 which receives the inner periphery of the armature 95. The notches I88 30 are slightly greater in length than the thickness of the armature 95, and hence permit a limited relative axial movement or play of the latter. In the event that the axial movement of the armature 95 exceeds the range permitted by the 35 notches I88, the pins 99 will be adjusted axially with the armature.

A plurality of friction plungers |8| are slidably mounted respectively in a series of radial bores I82, formed in the disk 33, and opening outwardly 40 into the inner sides of the bores 98. The plungers 8| are pressed outwardly against the sides of the pins 99 by compression springs I83 disposed in the bores I82, and exert a frictional drag which is effective to prevent ready displacement of the 5 pins, but which is not great enough to materially resist the movement of the armature 95 toward the electromagnet 98 when the latter is energized. Hence, each of the pins 99 constitutes a friction detent slidably disposed in the part 33 for 50 actuation by the part 95 upon movement of the latter in the closing movement of the clutch 29 through a distance in excess of a predetermined clearance, and in the reverse movement limiting the separation of the clutch elements to such 55 clearance.

When the electromagnet 98 is deenergized the armature 95 is free to move away a short distance the limits of which are determined by the ends of the notches I88 in the pins 99. No springs or other means are provided tending definitely to separate the electromagnet 98 and the armature 95. On the contrary, the armature is permitted a free-floating movement between the limits defined by the pins 99, and is caused to separate 65 slightly from the electromagnet 98 due to the relative rotation of the latter when the magnetic pull is discontinued. Thus the armature 95 may contact with the electromagnet 98, and is never separated from the latter by an air gap greater [0 than that permitted by the confines of the notches I88. The power requirements of the electromagnet 98 are therefore much more constant in closing the clutch 29 and then maintaining the latter in closed position than when both an air 75 gap and an opening pressure must be overcome. The electromagnet 90 in its preferred form comprises inner and outer concentric rings I04 and I05' of suitable material, and an annular 5 magnetic coil I06 interposed therebetween. An outer peripheral flange I'I integral with the ring I04 is secured to the outer ring I05, and constitutes a backing plate for one side of the coil I00.

A thin sheet I00 of non-magnetic material is interposed between the outer ring I and the flange I01 to interrupt thefiuxcircuit, so that any residual magnetism in the electromagnet 90 will be quickly eliminated after the latter is deenergized. It will be evident that the free sides of the rings I04 and I05 constitute pole faces adjacent the armature 95. A ring I09 of non-magnetic friction material adapted for engagement by the armature 95 is seated in notches I09 formed in the inner edges of the pole faces, and serves to enclose the adjacent side of the coil I03. The pole faces are substantially flush with the outer surface of the ring I09, but in use are likely to recede slightly due to wear.

The maximum possible air gap between the armature 95 and the friction ring I09, which constitute the coacting friction elements of the pilot clutch 29, remains constant regardless of wear. In the event of wear on the ring I09, movement of the armature 95 under the influence of the elec- 80 tromagnet 90 will cause a corresponding adjustment of the pins 99 against the action of the friction plungers IN. The length of the notches 99 exceeds the width of the armature 95 by an amount slightly greater than the sum of the end 35 plays of the driving and driven members 2I and 22. This difference defines the maximum possible air gap, which is possible only when the end plays are additive. The possible air gap is much less and-comparatively small when the end plays off- 40 set'each other. It will be understood that the armature 95 will not necessarily move from the electromagnet 90 through the full extent permitted by the notches 99.

Mounted on the electromagnet 90 for rotation 5 therewith, and extending in spaced relation about the armature 95 is a ring IIO (see Figs. 1, 6, and 7) of insulating material which is formed with an annular internal disk III extending in closed space relation about the disk 33. The disk III constitutes a carrier for a plurality of contact slip rings in the electric circuits for energizing the electromagnet 90. In the present instance, three slip rings H2, H3 and H4 are provided so that either of two circuits through the coil I06 may be utilized. The slip rings are mounted on the disk III in concentric relation about the shaft 22. One circuit (see Fig. 14) proceeds from the outer ring II2, through a line II5, the coil I05 and a line IIB to the inner ring H4. The other circuit has two parallel branches, one proceeding from the intermediate ring I I3 through a line I II, a normally closed switch I I8 and a line I I9 to the line H5, and the other proceeding from the line H1 through a line I20, an electrical resistance element I2I, and a line I22 to the line II5. From the line II5, the other circuit continues through the coil I06 and the line I I6 to the inner ring I I4. Three brush contacts I23, I24, and 125 are spring pressed respectively into sliding engagement with the slip rings II2, I I3, and I I4. These contacts are slidably disposed in guideways I26 (see Fig. 8) which extend perpendicularly to the contact faces of the rings H2, H3, and H4, and which are formed in an insulating block I21 7 mounted in a fixed position on the inside of the housing 20. Individual leaf springs I20, anchored to the block I21, are connected at their free ends to the brush contacts I23, I24, and I25, and urge the latter outwardly along the guideways I26.

The resistance element I2I preferably is annular in form, and is mounted in an annular groove I29 in the outer periphery of the insulating ring H0.

The two circuits through the coil I05 are selectively available as will be more fully described hereinafter. Normally, the electromagnet 90 has sufficient power, regardless of which circuit is selected, to close the pilot clutch 29 with enough force to effect the closing of the main clutch 25 against the resistance of the springs 56. However, if the switch circuit is selected, and the switch H3 is opened, the exciting current must pass through the resistance element I2I and the coil I06 in series. In this event, the power of the electromagnet 90 is greatly reduced, and, while still sufficient to hold the pilot clutch 29 in closed position, is not great enough to effect closing of the main clutch 20.

The switch H0 is adapted to be opened automatically when the driven shaft 22 overruns the motor shaft 2|. In the present instance, this is accomplished by utilizing the pilot clutch 29 to adjust theangul-ar position of the electromagnet 90 on the rim 08 to the extent permitted by the grooves 89. An annular plate I30 is secured in fixed position against one side of the disk 34, and extends outwardly beyond the outer periphery of the electromagnet 90. A portion of the outer margin of the plate I30 is cut away as indicated at I3I (see Figs. 6 and 7), and is bent laterally to define spaced lugs I32 and I33. 'A housing I34 enclosing the switch IIO is rigidly mounted on the outer periphery of the insulating ring I I0 for rotary movement with the electromagnet 90, and extends in spaced relation between the lugs I32 and I33. The switch II8 comprises a fixed contact I35 mounted on a bracket I30, and a movable contact I31 fixed on the free end of a leaf spring I38 anchored to a bracket I39. A coiled tension spring I40, anchored at opposite ends to the lug I32 and the housing I34, tends to rotate the electromagnet 90 into the position in which it is normally held by the frictional drag of the pilot clutch 29 when the electromagnet tends to drive the armature 95. Fixed on the other lug I33, and projecting tangentially of the plate I30 into the housing I34 for engagement with the free end of the leaf spring I38 to open the switch H8 is a pin I. It will be evident that when the armature 95 tends to rotate the electromagnet 90, the latter will be adjusted angularly against the action of the spring I40 through a limited extent, thereby causing the pin I4I to open the switch I I8. If the excitation of the electromagnet 90 is placed under the control of the switch I I8, the resistance element I2I will thereupon reduce the holding power as described, but not to a point where it is unable to overcome the spring I40.

Provision is made for confining a suitable lubricant in the screw device 30 and the bearing I4, and also to prevent any lubricant that may leak therefrom or from the gear case 24 along the shaft 22 into the housing 20 from entering between the friction surfaces of the main and pilot clutches 26 and 29. Referring first to the screw device 30, one end of the ball space is closed by means of an oil seal ring I42 (see Fig. 1) which is secured against the outer side of the ring 68 by a retainer I43, and which bears against the inner peripheral surface of the adjacent end of I theball bearing sleeve 15.

' I52 and I53 A similar ring I44 is secured to the disk 34 by a retainer I45. and bears in the adjacent end of the outer raceway 65 to seal the other end or the ball space.

In the ball bearing 14, an oil seal ring I46 is positioned in an annular notch I41 formed in the outer peripheral edge of one end of the inner sleeve 15, and bears against the inside of an annular guard plate I48 tightly secured to the adjacent end of the outer sleeve 11. The other end of the ball space is sealed by a fiat annular spring plate I48 which is secured at its outer peripheral edge in a notch in the outer bearing sleeve 11, and the inner peripheral edge of which is sprung into engagement in a notch in the inner sleeve 1.5.

Lubricant escaping from the bearing 14 or leaking inwardly along the shaft 22 to the clutch plate 28 is prevented from entering the main clutch 26 by a series of overlapping outer and inner oil guards I58 and lil, and I52 and I58. The outer oil guards I50 and II are of an annular truncated conical form, with their base ends secured respectively to the adjacent inner sides of the plates 31 and 5I, and with their small ends extending inside of the movable clutch plates 21 to points closely adjacent the opposite sides of the intermediate plate 28. A plurality of annularly spaced apertures I54 and I55 open from within the guards I58 and lil respectively through the plates 31 and 5|, and are outwardly inclined relative to the axis of rotation to facilitate the removal of collecting lubricant therethrou h by centrifugal force. The inner guards are also of an annular truncated form, and are secured at their small ends respectively to opposite sides of the intermediate plate 28. Hence, any lubricant that may find its way to either side of the plate 28 will be baiiled outwardly along the guards I52 and I58 into the guards I50 and I5I, and from there will be expelled through the apertures I54 and I55 to the external spaces where it can do no harm.

Lubricant finding its way between the elements of the pilot clutch 28 is adapted to be caught by an annular undercut flange I56 formed on the inner face of the disk 34, and overlapping the adjacent end of the disk 38. A plurality of annularly spaced apertures I51 opening from within the flange I58 through the disk 84 and the plate I30, and inclined outwardly relative to the axis of rotation are provided to expel the lubricant to the space outside of the clutch 28-. The outer end of the disk 33 is formed about the bearing 88 with an annular recess I58 which is flared outwardly to throw any lubricant leaking thereto beyond the central opening of the disk III.

The clutch mechanism Just described may be adapted to many different uses. If intended for use merely as a separable connection in a power transmission wherein either of the shafts 2i and 22 is adapted to drive the other in either direction, the electromagnet 80 may be rigidly fixed on the disk 34, and the switch H8 and associated parts may be dispensed with. The clutch mechanism is particularly adapted for use in the power drives of motor vehicles. Although of a unitary character, it is adapted for optional control whereby to obtain either a conventional drive, or automatic free wheeling under the control of the accelerator.

Any suitable type of control may be provided. In one form, illustrated in Fig. 15, the operating parts are mainly mechanical. The preferred form of the control, however, is fully electrical as illustrated in Fig. 14.

Referring first to Fig. 14, the conventional drive is subject to the actuation of a clutch pedal Ill pivotally mounted on the floor board I80 of the vehicle, and supplanting the mechanical clutch pedal ordinarily employed. The pedal I58 normally is urged upwardly by a spring I". Rigid with the pedal I58 is a switch arm I62 carrying a contact I63 which in its uppermost position engages a fixed contact I64. Upon depressing the pedal I58, the contact I63 is moved from the contact I64 onto a rheostat I84, then progressively along the latter to gradually increase the resistance, and finally into its lowermost position to break the electrical connection. Since the forces which it is required to handle are very small as compared with those of the ordinary clutch pedal, the pedal I58 is made in a design similar to that of the usual throttle pedal.

Assuming that the lever I58 is up so that the contacts I66 and I64 are in engagement, the conventional drive circuit for the electromagnet 88 is completed as follows: from the battery I65, through a line I66, the arm I62. the contacts I68 and I64, a line I61, a choke coil I68, a line I68, a switch I18, a line I1I, the slip ring II2, the line Hi, the coil I66, the line II6, the slip ring II4, a line I12 to the ground. When the pedal I59 is in its lowermost position, the circuit is broken.

Normally, the clutch pedal I58 is operated in the same manner as the ordinary clutch pedal. Thus, it is fully depressed to open the clutch 26 and is gradually released to close the clutch. In the initial upward movement of the pedal I58 into an intermediate position, the circuit is closed immediately from the contact I63, through the rheostat I I54 and a line I13 to the line I68, thereby shunting the choke coil I68. Obviously, the resistance in the circuit is progressively decreased, and hence the force of the clutch engagement is correspondingly increased as the pedal I58 continues its upward movement. This characteristic is of considerable advantage in that it permits substantially the entire stroke of the pedal I58 to be utilized in controlling the action of the clutch, for example to allow a certain amount of slippage to occur. The ordinary clutch pedal does not aiford the same degree of control since only a small portion of its stroke is available to vary the pressure on the friction surfaces of the clutch, and since it assumes some intermediate position, constantly subject to change and diificult to ascertain, when the clutch engages.

The switch H8 is not included in the conventional drive circuit, and hence the pilot clutch 29 will close the main clutch 26 regardless of whether or not the driven shaft 22 initially is over-running the motor shaft 26.

The clutch mechanism may be rendered automatic to obtain free wheeling by shifting the control from the pedal I58 to a pedal I16 connected to the fuel throttle. This may be accomplished by opening the switch I10, which is mounted on the dash I15, to interrupt the conventional drive circuit.

The throttle pedal I14 is pivotally mounted on the fioor board I68, and normally is urged toward its uppermost position by a spring I16. Rigid with the pedal I14 is a suitable switch arm I1? carrying a contact I18 which is movable from an open position downwardly over a rheostat I18 of progressively decreasing resistance. Assuming that the clutch pedal I58 is in its uppermost position and that the throttle pedal I14 is partially depressed, the-free wheeling circuit then is completed as follows: from the battery I65. through the line I66, the arm I62, the contacts I63 and 5 I64, the line I61, the choke coil I68, the line I69, the rheostat I19, the contact I18, the arm I11,.a line I80, the slip ring II3, the line II1, the switch H8, the line II9, the coil I06, the line II6, the slip ring I I4, and the line I12 through the ground back to the battery I65. If the driven shaft 22 is not over-running the motor shaft 2I, the electromagnet 90 will be energized to its full power to close the main clutch 26 just as when in conventional operation. However, if the shaft 22 is over-running the motor shaft 2I, the electromagnet 90 will be adjusted angularly to open the switch H8, and thereby require the current to flow from the line II1, through the line :I20, the resistance element I2I, and the lines I22 and H5 to the coil I06. Thereupon, the power of the pilot clutch 29, although suflicient to maintain the switch I I8 open, is'reduced to such an extent that the main clutch 26 will remain open.

Thus, the operation of the main clutch 26 is under the joint automatic control of the throttle pedal I14 and the relative speedof the motor 23 and the vehicle. When the throttle pedal I14 is depressed, the circuit for the electromagnet 90 is closed. If the speed of the motor 23 is less than that of the vehicle, the main clutch 26 will remain open, and free wheeling will occur. Upon acceleration of the motor 23, the main clutch 26 will close if and when the speeds of the driving and driven shafts 2I and 22 are synchronized. Hence, there can be no appreciable shock or clutch slippage when the motor 23 picks up the load, and therefore no appreciable wear on the friction surfaces due to free wheeling. When the throttle pedal I14 is up, the main and pilot 40 clutches 26 and 29 will both be open, and hence free wheeling will occur"if the vehicle is in motion. Although the clutch mechanism is under the control of the throttle pedal I14, the main clutch 26 may be opened at any time by fully de- 45 pressing the clutch pedal I59.

The choke coil I68 is provided in the free wheeling circuit, so that, when the throttle pedal I14 is depressed, there will be a short delay in the closing of the main clutch 26 to allow time for 50 the motor 23 to accelerate slightly before the drive connection is established. The purpose of this delay is to prevent any likelihood of the motor 23 becoming stalled when the vehicle is not in motion. The duration of the delay is varied 55 automatically in accordance with the degree of throttle opening by reason of the rheostat I19, and hence with the rate at which the motor 23 is accelerated. This is due to the fact that the choke coil I68 will build up to a given current a; more quickly when the resistance is reduced or out entirely than when the latter is relatively high. When the throttle pedal I14 is but slightly depressed, only a little power is .given to the motor 23, and hence the delay is relatively pro- 55 longed. Conversely, when the throttle pedal I14 is fully depressed, the rheostat I19 is cut out of the circuit, so that the delay is comparatively slight. For intermediate positions of the throttle pedal I14, the delay is varied accordingly.

7 Not only does the rheostat I19, under the control of the throttle pedal I14, vary the delay of the clutch engagement, but it also determines the final value of the electric current through the electromagnet 90, and hence the pressure of the 7 clutch engagement in accordance with the power delivered by the motor 23. This has the advan-.

tage that, when starting from rest, if the throttle pedal I14 is depressed but a short distance s) that the motor 23 is delivering comparatively little power, the main clutch 26 will be engaged with a corresponding pressure, thereby permitting more slippage, and hence affording a smooth and easy start and. avoiding any possibility of stalling.

In some instances, as for example when driving in heavy traific, or when starting after a traffic signal change. it may be desired to engage the clutch 26 more quickly than normally permitted by the choke coil I68. This may be accomplished under the joint control of the two pedals I59 and I14, 1. e. by first fully depressing the clutch pedal I59, then depressing the throttle pedal I14 to speed up the motor 23 and decrease the resistance of the rheostat I19 inthe clutch circuit, and then allowing the clutch pedal to rise graudally as in the conventional drive. Thus.- the free wheeling circuit will be closed without passing through the choke coil I68, and the delay in engaging the clutch 26 normally caused by the coil will be avoided.

The conversion of the control from free wheeling to a. conventional drive or vice versa is accomplished simply by closing or opening the dash switch I10. In the first instance, the throttle pedal I14 is partially depressed to speed up the motor 23 (assuming the vehicle is in motion) so as to approximately synchronize the speeds of the driving and driven shafts 2I and 22; then the clutch pedal I59 is completely depressed to open the clutch circuit; now the switch I10 is closed to prepare the conventional drive circuit: and finally the clutch pedal is gradually released Io gently engage the clutch 26. In this. manner, the conversion may be accomplished without shock. If a sudden need should arise to utilize the braking power of the motor 23 in order to avoid an accident, the switch I10 may be closed Without depressing either pedal, and in this event the electromagnet 90 will be fully energized immediately, and the clutch 26 will be closed'under full pressure. A considerable shock may result if the vehicle is moving rapidly and coasting, but this shock is of course acceptable if the object sought is to avoid an accident, and in any event is the worst that can result from mishandling of the control by the operator, and is not as severe as that produced when closing the jaw clutch to eliminate the over-running clutch in commonly used free wheeling systems to connect driving and driven parts having a high velocity relative to each other. The shock may be reduced or eliminated by momentarily accelerating the motor 23 just before the switch I10 is closed.

Figs. 15 and 16 illustrate a modified mechanical control mechanism for the pilot clutch 29. In this form, the electromagnet circuits across the slip rings H2, H3, and H4 are the same as in the first form, and hence are identified by the same reference characters. The mechanical form comprises a. clutch pedal I8I and a throttle pedal I82, both of which are pivotally mounted on the floor board I60 0! the vehicle, and a carbon pack rheostat I83 taking the place of the rheostats I64 and I19. Both pedals I8I and I82 are spring pressed into their uppermost positions. The rheostat I63 is adapted to open when released, and to provide a gradually decreasing resistance as it is progressively compressed. It is under the exclusive control of the clutch pedal I8I when the system is in conventional drive, and under closed.

the Joint or individual control of both pedals I9I and I92 when the system is set for free wheeling.

When the clutch pedal I9I is released, the conventional drive circuit is adapted to be completed from the battery I94, through a line I99, the carbon pack rheostat I99, a line I99, 8. switch I91 corresponding to the switch I19, a line I99 to the slip ring H2, and from there through the coil I99 back to the battery as previously described. The free wheeling circuit is always established from the line I99 to the slip ring H9, and from there through either the switch H9 or the resistance element I2I to the coil I99, but is ineffective as long as the switch I" is Thus, if the switch I I9 were to be opened, the conventional drive circuit paralleling the resistance element I2I would still ensure a full energization of the electromagnet 99.

The movable element of the rheostat I99 has a plunger I99 pivotaily connected to an eccentric pin I99 on one end of a rock shaft I 9| suitably Journaled in a fixed position. Fixed on the shaft -I9I are two laterally extending arms I92 and I99.

The free end of one arm I92 is rounded, and is connected by a pin I94 to a contractile spring I95 tending to rock the shaft I 9| in a direction to compress the rheostat I99. The other arm I99 is adapted for engagement by 2. prong I99 extending rearwardly from the clutch pedal I9I to rock the shaft I9I against the action of the spring I95.

Suitable means is provided for retarding the rocking of the shaft I 9I under the action of the spring I95, but is rendered inoperative when the clutch pedal I9I is actuated to control the clutch 29. In the present instance, this means comprises a dash pot I96 having a diaphragm I91 permitted to move freely and quickly in one direction, but restricted to a comparatively slow movement in the opposite direction by the action of a check valve with an exhaust bleed opening. A lever I99 is pivotally connected at one end to the diaphragm I91, and at its other end is formed with a transverse notch I99 adapted to engage the free rounded end of the arm I92. The lever I99 is urged toward the arm I92 by a contractile spring 299. A prong 29I extending rearwardly from the clutch pedal I9I is adapted to engage the toe of the lever I98 to disengage the notch I99 from the arm I92 against the action of the spring 299 in the initial downward movement of the clutch pedal.

The clutch pedal I9I affords a conventional control in the same manner as the ordinary standard pedal. When the pedal I9! is depressed, the prong 29I disengages the lever I98, and the prong I96 acts against the arm I93 to relieve the pressure on the rheostat I93, and thereby to open the conventional drive circuit. As a result, the main clutch 29 is opened. When the clutch pedal I9I is up, the rheostat I99 is compressed, and hence the main clutch 26 is closed at full pressure. The present control is distinguished from the ordinary control in that, as the pedal I9I is gradually released, the shaft I9I is permitted to rock so as to vary the pressure on the rheostat I93 progressively over substantially the entire stroke of the pedal, thereby affording means for accurately adjusting the pressure of clutch engagement to suit the driving requirements.

The clutch 26 may always be opened by the pedal IN, and may also be placed under the control of the throttle pedal I 92 for free wheeling. To this end, a link 292 is pivotally connected at one end to the rear of the throttle pedal I92, and at the other end has a pin 299 with a square longitudinal notch 299 in one side adapted to be positioned for engagement with a third arm 295 fixed on the rock shaft I9I. When the throttle pedal I92 is released, the pin 294 engages the arm 299 to rock the shaft I9I, and thereby to relieve the pressure on the rheostat I99. Conversely, upon depressing the throttle pedal I92, the am 295 is released to permit pressure to be applied to the rheostat I93. Assuming that the clutch pedal I9I is permitted to remainin its uppermost position. the lever I99 will remain in-engagement with the arm I 92, and hence the dash pot I96 will damp the movement of the shaft I9I so as to delay the closing of the clutch 29 until the motor 23 has accelerated slightly in response to the initial depression of the throttle pedal I92. However, the dash pot I99 is incapable of retarding the reverse rotation of the shaft I9I upon releasing the throttle pedal I92. The delay in closing the clutch 29 may be eliminated, if desired, by first partially depressing the clutch pedal I9I to disengage the lever I99, and then depressing the throttle pedal I92 to release the arm 295 for follow up movement.

The pressure of clutch engagement varies in accordance with the position of the throttle pedal I 92. Thus, as the pedal I92 is progressively depressed, the arm 295 follows the pin 293, as will be evident in Fig. 16, and effects a corresponding decrease in the resistance in the exciting circuit. Consequently, when the fuel throttle is wide open so that the motor can develop a heavy driving torque, the pressure of clutch engagement is at a maximum. For smaller throttle openings, correspondingly lighter pressures are obtained.

The conversion from conventional drive to free wheeling and vice versa is effected respectively by opening the switch I91 and interposing the pin 293 in the path of the arm 295 and by closing the switch and withdrawing the pin out of the reach of the arm. Thus, the switch I9! is operable by a rock shaft 296 on which is also fixed an arm 291 having a longitudinal slot 298 slidably receiving the pin 293. A button 299 adjustable on the dash is connected through a wire 2I9 to the arm 29?. The button 299 is adapted to be yieldingly secured in either of two positions. In one position of the button, the system is set for free wheeling. In the other position, the arm 29'! serves to hold the pin 293 out of the range of the arm 295.

When set for free wheeling, the clutch 26 may be opened by either depressing the pedal fill or releasing the pedal I82. If the clutch pedal ISI is fully up, depressing the throttle pedal I82 will effect a delayed closing of the clutch 26. If the clutch pedal I9I initially is partially depressed to release the arm I92 from the lever I98, the clutch 29 will be closed immediately upon depressing the throttle pedal I82. Upon releasing both pedals IN and I92, engagement between the arm I92 and the lever I99 will be automatically reestablished.

I claim as my invention:

1. A clutch mechanism comprising, in combination with a driving member and a normally driven member, a flywheel secured to said driving member and having an annular rim, an annular lar friction disks splined to the interior of said rim for movement axially of said driving member, spring means tending to separate said disks axially respectively against said flywheel and said plate, a friction disk located between said first mentioned disks and splined for axial movement on said driven member, a plurality of pins each having opposed shoulders movable in opposite directions respectively into engagement with the outer sides of said first mentioned disks to compress all of said disks selectively against said flywheel or said plate, and means for actuating said pins out of an intermediate position in either direction.

2. A clutch mechanism comprising, in combination with a driving member and a normally driven member, two opposed stops mounted in fixed position on one of said members and spaced axially thereof, two friction disks splined for axial movement between said stops on one of said members, a-friction disk splined for axial movement between said first mentioned disks on the other of said members, spring means tending to separate said disks, and actuating means movable in opposite directions to compress said disks into driving engagement respectively against one or the other of said stops.

3. A clutch mechanism comprising, in combi- 2 nation with a driving member and a normally driven member, two opposed stops mounted in fixed position on one of said members and spaced axially thereof, two friction disks mounted for independent axial movement between said stops.

ball bearing splines for connecting said disks for rotation with one of said members, a friction disk splined for axial movement between said first mentioned disks on the other of said members, spring means tending to separate said disks, and

actuating means movable in opposite directions to compress said disks into driving engagement respectively against one or the other of said stops.

4. A clutch mechanism comprising, in combination with a driving member and a normally driven member, two opposed stops mounted in fixed position on one of said members and spaced axially thereof, two friction disks splined for axial movement between said stops on one of said members, a friction disk splined for axial movement between said first mentioned disks on the other of said members, spring means tending to separate said disks, two outwardly flared annular oil guards mounted respectively on said stops and extending through said first mentioned disks closely to opposite sides of said last mentioned disk, said strips being formed with oil outlets immediately within the confines of said guards, two outwardly flared annular oil guards mounted respectively on opposite sides of said last mentioned disk and extending into said first mentioned guards, and actuating means movable in opposite directions to compress said disks into driving engagement respectively against one or the other of said stops.

5. A clutch mechanism comprising, in combination with a driving member and a normally driven member, a clutch for connecting said members, a triple thread screw element and a mating nut element, one of said elements being constrained for rotation with said driving member and being axially movable to actuate said clutch, the other of said elements being anchored against axial movement, three ball bearings in engagement between the respective threads of said elements, means for retaining said balls in a common transverse plane, and means for rotating said elements relatively to each other.

6. A clutch mechanism comprising, in combi-- nation with a driving member and a normally driven member, a clutch for connecting said members and having driving and driven clutch members movable axially in opposite directions into driving engagement, a screw element and a nut element having mating screw threads, an actuator for said clutch having a universal rocking connection with one of said elements, the other of said elements being anchored against axial movement, and means for rotating said other element relatively to said one element out of an intermediate position in either direction to effect the closing of said clutch.

7. A clutch mechanism comprising, in combination with a driving member, and a normally driven member, a clutch having coacting driving and driven frictiondisks splined for axial movement respectively on said members and being compressible in either direction into driving engagement, spring means tending to separate said disks, a screw, an end thrust anti-friction bearing anchoring said screw against axial movement in either direction relative to said driving member, a nut rotatable about said screw, a plurality of balls interposed between the threads of said screw and nut, an actuator plate mounted on said nut for rotation and axial movement therewith and being movable axially in either direction out of an intermediate position to close said clutch, and means for rotating said screw in said nut, said spring means tending to return said actuator plate into said intermediate position when said last mentioned means is rendered inoperative.

8. A clutch mechanism comprising, in combination, a main clutch, an anti-friction screw device movable in either direction out of an intermediate position to close said main clutch,

, in bearing engagement therebetween, said screw device being operable in either direction out of an intermediate position to close said clutch against the action of said spring means, a pilot clutch having coacting clutch members respectively connected to said driven shaft and one of said elements and operable to actuate said screw device in one direction when said driving shaft overruns said driven shaft and in the other direction when said driven shaft overruns said driving shaft, and means for closing said pilot clutch.

10. A clutch mechanism comprising, in combination, a driving shaft and a normally driven shaft, a main clutch having coacting clutch members respectively connected to said shafts and having spring means tending to open said members, an anti-friction screw device having a screw element, a nut element and a plurality of balls in bearing engagement therebetween, said screw device being operable in either direction out of an intermediate position to close said clutch against the action of said spring means, a pilot clutch having coacting clutch members respectively connected to said driven shaft and one of said elements and operable to actuate said screw device in one direction when said driving shaft overruns said driven shaft and in the other direction when said driven shaft overruns said driving shaft, means for normally closing said pilot clutclnand means available at will for rendering said last mentioned means ineffective when said driven shaft overruns said driving shaft.

11. A clutch mechanism comprising, in combination with a driving shaft and a driven shaft, a clutch for connecting said shafts, power multiplying means operable in either direction out of an intermediate position to close said clutch, an electromagnetic pilot clutch for actuating said means upon relative rotation between said shafts, and means for normally closing said pilot clutch,

said last mentioned means being adjustable at will to automatically prevent said pilot clutch from being closed when said driven shaft overruns said driving shaft.

12. A clutch mechanism comprising, in combination, a driving shaft and a normally driven shaft, a main clutch having coacting clutch members respectively connected to said shaftsand having spring means tending to open said members, power multiplying means operable in either direction out of intermediate position to close said clutch and tending to return into said position in response to said spring means, an electromagnetic pilot clutch having an electromagnet and an armature connected respectively to said means and said driven shaft and constituting coacting pilot clutch members, an exciting circuit for said electromagnet including a resistance and a switch in parallel, and means for closing said circuit, said switch being adapted to open automatically in response to overrun by said driven shaft to reduce the power of said electromagnet below that required to overcome said spring means.

13. A clutch mechanism comprising, in combination with a driving shaft and a coaxial driven shaft, a member mounted for rotation with one of said shafts, an annular electromagnet mounted for limited rotation on said member, an armature mounted for rotation on the other of said shafts, said electromagnet and armature constituting clutch elements movable axially into and out of coacting engagement and adapted upon relative rotation of said shafts in opposite directions to adjust said electromagnet respectively in its opposite limit position on said member, an electric circuit for energizing said electromagnet to effect full driving pressure between said elements and including a switch adapted to be opened automatically upon movement of said electromagnet into one limit position, spring means tending to retain said electromagnet in its other limit position, and a parallel circuit for energizing said electromagnet to effect a drag between said elements of suflicient force to overcome said spring means when said switch is open.

14. A clutch mechanism comprising, in combination with a driving shaft and a coaxial driven shaft, a member mounted for rotation with one of said shafts, an annular electromagnet mounted for limited rotation on said member, an armature mounted for rotation on the other of said shafts, said electromagnet and armature constituting clutch elements movable axially into and out of coacting engagement and adapted upon relative rotation of said shafts in opposite directions to adjust said electromagnet respectively in its 0pposite limit position on said member, electric circuits for energizing said electromagnet to effect engagement between said elements, and means automatically responsive to adjustment of said electromagnet respectively into said limit positions for varying the power of said electromagn t,

of said elements and being self-adjustable to compensate for wear on said elements.

16; A clutch mechanism comprising, in combination, an electromagnetic clutch having an electromagnet and a coacting armature relatively movable thereto, an energizing circuit for said' electromagnet, and a choke coil and a variable resistance switch in series in said circuit.

17. A clutch mechanism for the drive from a motor having an adjustable fuel throttle, said mechanism comprising, in combination, an electromagnetic clutch having an electromagnet and a relatively movable armature, an energizing circuit for said electromagnet, said circuit including a normally closed switch and a normally open variable resistance switch in series, a manual actuator for said throttle,'said last mentioned switch being operable by said actuator to close said circuit and to decrease the resistance as said throttle is opened progressively, and a manual actuator for opening said first mentioned switch.

direction from said fixed contact onto and along said rheostat to insert a progressively increasing resistance in said circuit, and then into an open position.

19. A clutch mechanism comprising, in combination, a main friction clutch, power multiplying means for actuating said clutch, an electromagnetic pilot clutch for actuating said means, and two parallel circuits selectively available for energizing said pilot clutch, one circuit including in series a normally closed variable resistance switch, and a normally closed conversion switch, and the other circuit including in series said first mentioned switch and a normally open variable resistance switch.

20. A clutch mechanism for the drive from a motor having an adjustable fuel throttle, said mechanism comprising, in combination, an electromagnetic friction clutch, and an energizing circuit for said clutch, said circuit including a normally open variable resistance switch operable by said throttle to decrease the resistance as the throttle is opened.

21. A clutch mechanism comprising, in combination, an electromagnetic clutch having an electromagnet and a relatively movable armature, an energizing circuit for said electromagnet and including a variable resistance, means normally operable to decrease said resistance, mechanical means for controlling said last mentioned means and progressively adjustable to permit corresponding degrees of operation of said first mentioned means, and a time delay device for damping the operation of said first mentioned means.

22. A clutch mechanism comprising, in combination, an electromagnetic clutch having an electromagnet and a relatively movable armature, an energizing circuit for said electromagnet and including a variable resistance, means normally operable to decrease said resistance, mechanical means for controlling said last mentioned means and progressively adjustable to permit corresponding degrees of operation of said first mentioned means, a time delay device for damping the operation of said first mentioned means, 1 means available at will for rendering said second mentioned means inoperative, and a second mechanical means progressively adjustable to permit corresponding degrees of operation of said first mentioned means while maintaining said time delay device inoperative.

23. A clutch mechanism comprising, in combination, a main friction clutch, power multiplying means for actuating said clutch, an electromagnetic pilot clutch for actuating said means, and

a circuit for energizing said pilot clutch and including a variable resistance, means including a manual actuator for closing said circuit and progressively decreasing said resistance, a time delay device for retarding said decrease in resistance, and a second manual actuator available at will for rendering said time delay device inoperable.

24. A clutch mechanism comprising, in combination with a driving member and a normally driven member, a plurality of axially spaced friction disks adapted for relative movement into and out of engagement, alternate disks being connected respectively to said members, two outwardly flared annular oil guards mounted on one of said members respectively at opposite sides of said disks, two outwardly flared annular oil guards mounted for rotation with the other of said members and extending oppositely into said first mentioned guards, and means for actuating said disks into driving engagement, said guards being operable to deflect and direct oil out of said clutch mechanism.

25. A clutch mechanism comprising, in combination with a driving member and a normally driven member, a clutch for connecting said members and having driving and driven clutch members movable axially into and out of driving engagement, a screw element and a nut element having coacting screw threads, an actuator 60 for said clutch having a universal rocking connection with one of said elements, the other of said elements being anchored against axial movemerit in one direction, and means for rotating said other element relatively to said one element to effect the closing of said clutch.

26. A clutch mechanism comprising, in combination with a driving member and a driven member,-'a main clutch having a plurality of friction elements adapted to be pressed axially into frictional driving engagement, certain of said elements being connected to one of said members and others of said elements having an anti-friction ball spline connection with the other of said members, an anti-friction non-locking ball screw 65 device movable in either direction out of an intermediate position to close said main clutch, and a pilot clutch for actuating said screw device.

27. A clutch mechanism comprising, in combination with a driving shaft and a driven shaft, a 70 clutch for connecting said shafts, power multiplying means operable in either direction out of an intermediate position to close said clutch, a

pilot clutch for actuating said means upon relative rotation between said shafts, and means for 75 normally closing said pilot clutch, said last mentioned means being adjustable at will to automatically prevent said pilot clutch from being closed when said driven shaft overruns said driving shaft.

28. A clutch mechanism comprising, in combination, a driving shaft and a normally driven shaft, a main clutch having coaoting clutch members respectively connected to said shafts, and an electromagnetic pilot clutch for operating said main clutch, said pilot clutch comprising an electromagnet for operating said main clutch and'an armature connected to said driven shaft, an exciting circuit for said electromagnet including a resistance and a switch in parallel, and means for closing said circuit, said switch being adapted to be opened automatically in response to overrun by said driven shaft to reduce the power of said electromagnet below that required to close said main clutch.

29. In a clutch mechanism, in combination with a driving member and a driven member, a disk secured for rotation with one of said members, an electromagnet mounted on said disk for relative rotation through a limited degree, spring means tending to urge said electromagnet into one position of adjustment on said disk, a switch controlled by said electromagnet and adapted to be actuated automatically between open and closed position upon movement of said electromagnet from one extreme position to the other on said disk, a circuit including said switch for controlling the excitation of said electromagnet, and an armature connected to the other of said members and adapted for relative axial movement into frictional engagement with said electromagnet, said electromagnet and said armature constituting the elements of a clutch.

30. In a clutch mechanism comprising, in combination with a driving member and a driven member, two friction elements connected respectively to said members and movable axially into and out of frictional engagement, one of said elements comprising a part fixed to one of said members and a second part splined to said first mentioned part for axial movement, a friction detent slidably disposed in one of said parts for actuation by the other of said parts upon movement of the latter in the closing movement of the clutch through a distance in excess of a predetermined clearance, and in the reverse movement of said part limiting the separation of said elements to said clearance.

31. In a clutch mechanism comprising, in combination with a driving member and a driven member, an end face friction clutch element secured to one of said members, a disk secured to the other of said members, an annular friction element splined to the periphery of said disk for axial movement into and out of frictional engagement with said first mentioned element, a friction guideway in said disk extending parallel to the axis of rotation, a friction plunger slidable in said guideway and having a notch receiving said annular element, said notch permitting a limited relative axial clearance movement of said annular element, and means for imparting a friction drag to said plunger, whereby upon movement of said annular element into engagement with said first mentioned element through a distance greater than said clearance, said plunger will be moved therewith against the resistance of said last mentioned means, and upon movement of said annular element away from said first mentioned element, said plunger will limit the separation of said elements to said clearance.

32. In a control for a clutch mechanism comprising, in combination with a control circuit, a carbon pack rheostat in said circuit, means tending to operate in one direction to place said rheostat under compression, and a clutch pedal for controlling said last mentioned means.

33. In a control for a clutch mechanism comprising, in combination with a control circuit, a carbon pack rheostat in said circuit, means including a rock shaft tending to rotate in a direction to place said rheostat under compression, a dash pot, releasable means connecting said dash pot and said shaft to retard the action of said first mentioned means, and a spring actuated manual clutch pedal operable to disengage said releasable means and to operate said first mentioned means in the other direction to relieve said rheostat of compression.

34. In a control for a clutch mechanism comprising, in combination with a control circuit, a carbon pack rheostat in said circuit. means including a rock shaft tending to operate in one direction to place said rheostat under compression, a dash pot, releasable means connecting said dash pot and said shaft to retard the action of said first mentioned means, a pedal automatically operable in one direction to actuate said first mentioned means in a reverse direction to relieve said rheostat of compression, and a clutch pedal for disengaging said releasable means.

HOWARD D. COLMAN. 

